Normally, when I find myself in this same situation, I ask the front seat passenger to hold the steering wheel while I crawl out the sunroof and hang on the roof rack for 5 miles or so before I crawl back in, push the clutch pedal to the floor (this cancels the cruise control), move the shift lever to the next lowest gear range, and reengage the clutch at the very instant that the engine rpms have dropped to the appropriate amount for the vehicle speed in the gear I am shifting into. If you find this doesn't solve your problem, please ask THC or Tony for a better explanation.